A significant problem in freezing organs is the need for a substitute for cryo-precipitated plasma which is used pre- and post freezing. Various colloid solutions will be substituted for the plasma and weight gain of the kidney compared with that using the plasma. LDH and GOT levels in the venous effluent are already used to assay in vitro renal damage following freeze-thawing. A similar study will now be done to correlate electrolyte changes as a measure of renal damage. While microwave thawing is the only way to achieve quick thawing, the microwaves may do intrinsic damage to the kidney. Electronmicroscopy will be used to assess such damage at various power outputs and frequencies when kidneys are thawed from 75 degrees Centigrade. Observations on using increasing concentrations of cryoprotective agents during freezing and decreasing concentrations during thawing will continue. BIBLIOGRAPHIC REFERENCES: Kubota, S., Crabo, B. G.,. and Lillehei, R. C.: Interaction of cooling rate, warming rate, and concentration of DMSO on survival of the frozen canine kidneys. The . physiologist 18, 280, 1975.